Hazard Assessment With Environmental Compatibility of Ferrochrome Wastes in Their Utilization Aspect

Ferrochrome slag (FCS) and ferrochrome flue dust (FFD) are the two major solid wastes generated in the production of ferrochrome alloy. Physical and mechanical studies reveal better properties so that these can be gainfully utilized in many construction fields, particularly as aggregate in concrete works. However, the chemical properties reveal about 11.2% and 20.3% residual hazardous chromium (as Cr₂O₃) in FCS and FFD, respectively. Incidentally, almost all the chromium in these wastes remains inherently entrapped as trivalent and metallic forms with little chance of leaching of soluble hexavalent chromium from the wastes. However, the preliminary toxicity characteristic leaching procedure (TCLP) analysis result identifies the FFD as hazardous waste as it fails to satisfy the TCLP standard with respect to chromium. But in situ, voluminous FCS waste after satisfactory TCLP compliance can be utilized and disposed of. However, the leaching studies of FCS under adverse conditions such as reduced particle size and low pH demonstrate the release of a significant amount of leachable hexavalent chromium. As such, it still satisfies the TCLP standard for chromium and thus comes out of the purview of hazardous waste. However, it fails to meet the regulatory criteria of Indian discharge standards to surface water bodies with respect to hexavalent chromium, thereby restricting its usage potential and disposal consideration.